Plasma processing device and method of monitoring plasma discharge state in plasma processing device

ABSTRACT

An object is to provide a plasma processing device capable of rightly monitoring existence of plasma discharge and also rightly monitoring existence of abnormal discharge. Another object of the present invention is to provide a method of monitoring a state of plasma discharge in the plasma processing device. 
     A discharge detection sensor  23 , in which a dielectric member  21  and a probe electrode unit  22  are combined with each other, is attached to an opening portion  2   a  provided in a lid portion  2  composing a vacuum chamber. A change in the electric potential induced in the probe electrode  22   b  according to a change in plasma discharge is received, electric potential change wave-forms of specific patterns are respectively detected by an N-type wave-form detecting portion  34  and V-type wave-form detecting  35 , and a discharge state judgment including a judgment of whether the electric discharge exists or does not exist and whether the electric discharge is normal or abnormal is made according to a counted value of counting the number of times of appearance of these electric potential change wave forms for each type of wave-form by a discharge ON wave-form counter  36 , a discharge OFF wave-form counter  37 , an abnormal discharge wave-form counter  38  and a leak discharge wave-form counter  39.

TECHNICAL FIELD

The present invention relates to a plasma processing device forexecuting plasma processing for an object to be processed such as aboard. The present invention also relates to a method of monitoring aplasma discharge state for monitoring whether the plasma discharge isexecuted or not in the plasma processing device or whether the plasmadischarge is normal or abnormal.

BACKGROUND ART

Plasma processing is well known as a surface processing method forexecuting cleaning or etching upon an object to be processed such as aboard on which electronic parts are mounted. In plasma processing, aboard to be processed is put into a vacuum chamber forming a processingchamber. Then, plasma discharge is generated in the processing chamber.When ions and electrons generated as a result of the plasma dischargeare made to act on a surface of the board, predetermined surfaceprocessing is executed. In order to stably execute the plasma processingat high quality, it is necessary that plasma discharge is properlygenerated according to a condition of plasma discharge which has beenpreviously determined conforming to an object of processing. Therefore,for the object of monitoring a state of the generation of plasmadischarge, various means and methods have been conventionally employed.

For example, a method is known which detects an influence exerted uponvoltage or current of a high frequency power supply portion by a changein plasma discharge for some factors. Further, a method is known whichestimates a state of discharge when a self-bias voltage generatedbetween electrodes by plasma discharge is detected. However, thesemethods are disadvantageous as follows. In the case where it isnecessary to generate plasma discharge under the condition of lowoutput, the detection accuracy is low and it is difficult to accuratelydetect a state of plasma discharge. Due to the above disadvantages ofthe conventional methods, a method by which a change in the plasmadischarge state can be directly detected has been recently used.Concerning this matter, for example, refer to Patent Document 1. Thismethod detects the existence of abnormal discharge as follows. Adischarge detection sensor having a probe electrode for detectingelectric potential is attached into a vacuum chamber in which aprocessing chamber is provided. When a change in the electric potential,which is induced according to a change in plasma discharge in the probeelectrode is detected, whether or not abnormal discharge is caused inthe processing chamber is detected.

Patent Document 1: Official gazette of JP-A-2003-318115

According to this method, it is possible to highly sensitively detect achange in the state of plasma discharge generated in the processingchamber. Therefore, even when an output of the high frequency powersupply portion is low, it is possible in principle to properly monitorwhether or not plasma discharge is executed and it is also possible toproperly monitor whether or not the plasma discharge is abnormal.However, in the above Patent Document, a specific application example,which is necessary for highly accurately monitor existence of plasmadischarge and also highly accurately monitor existence of abnormaldischarge, is not clearly disclosed. Therefore, it has been desired todevelop a new application technique to be applied to an actual plasmadischarge device.

DISCLOSURE OF INVENTION

An object of the present invention is to provide a plasma processingdevice capable of rightly monitoring existence of plasma discharge andalso rightly monitoring existence of abnormal discharge. Another objectof the present invention is to provide a method of monitoring a state ofplasma discharge in the plasma processing device.

The present invention provides a plasma processing device for executingplasma processing for an object to be processed which is accommodated ina processing chamber, comprising: a vacuum chamber forming theprocessing chamber; an electrode portion arranged in the processingchamber; a vacuum exhaust portion for exhausting gas from the processingchamber by vacuum; a gas supply portion for supplying gas, which is usedfor generating plasma, into the processing chamber; a high frequencypower supply portion for generating plasma discharge in the processingchamber when a high frequency voltage is impressed upon the electrodeportion; a matching device for matching impedance of a plasma dischargecircuit for generating plasma discharge with impedance of the highfrequency power supply portion; and a plasma discharge state monitoringunit for monitoring a plasma discharge state in the processing chamber,the plasma discharge state monitoring unit including: a dischargedetection sensor having a plate-shaped dielectric member attached to thevacuum chamber so that one face of the plate-shaped dielectric membercan be opposed to the plasma discharge generated in the processingchamber and also having a probe electrode arranged on the other face ofthe plate-shaped dielectric member; a data processing portion operatingin such a manner that when the probe electrode receives a change in theelectric potential induced according to a change of the plasmadischarge, a wave-form of a change of electric potential of a specificpattern is detected in each of the first wave form monitoring time zonewhich is set including a timing of starting the impression of the highfrequency voltage, the last wave-form monitoring time zone which is setincluding a timing of the finish of impression of the high frequencyvoltage and the intermediate wave-form monitoring time zone which is setincluding a time zone interposed between the first wave-form monitoringtime zone and the last wave-form monitoring time zone and that thenumber of times of detection of the wave-form of a change of theelectric potential is counted for each wave-form monitoring time zoneand the counted value is held; and a judgment portion for judging astate of discharge including the judgment of whether or not the plasmadischarge is executed and whether the plasma discharge state is normalor abnormal.

The present invention provides a method of monitoring a plasma dischargestate in a processing chamber in a plasma processing device, the plasmaprocessing device including: a vacuum chamber forming the processingchamber; an electrode portion arranged in the processing chamber; avacuum exhaust portion for exhausting gas from the processing chamber byvacuum; a gas supply portion for supplying gas, which is used forgenerating plasma, into the processing chamber; a high frequency powersupply portion for generating plasma discharge in the processing chamberwhen a high frequency voltage is impressed upon the electrode portion; amatching device for matching impedance of a plasma discharge circuit forgenerating plasma discharge with impedance of the high frequency powersupply portion; and a discharge detection sensor having a plate-shapeddielectric member attached to the vacuum chamber so that one face of theplate-shaped dielectric member can be opposed to the plasma dischargegenerated in the processing chamber and also having a probe electrodearranged on the other face of the plate-shaped dielectric member,wherein an object to be processed is accommodated in the processingchamber and processed by means of plasma processing, the method ofmonitoring a plasma discharge state in a processing chamber in a plasmaprocessing device comprising: a step in which a change in electricpotential induced according to a change in the plasma discharge in theprobe electrode is received by a data processing portion; a step inwhich a wave form of a change of electric potential of a specificpattern is detected by a wave-form detecting portion in each of thefirst wave-form monitoring time zone which is set including a timing ofstarting the impression of the high frequency voltage, the lastwave-form monitoring time zone which is set including a timing of thefinish of impression of the high frequency voltage and the intermediatewave-form monitoring time zone which is set including a time zoneinterposed between the first wave-form monitoring time zone and the lastwave-form monitoring time zone; a step in which the number of times ofdetection of the potential change wave-form is counted for eachwave-form monitoring time zone and the counted value is held; and a stepin which a plasma discharge state judgment, which includes the judgmentof whether or not the plasma discharge is executed and also includes thejudgment of whether the plasma discharge state is normal or abnormal, ismade according to the counted value of each wave-form monitoring timezone.

The present invention provides a plasma processing device for executingplasma processing for an object to be processed which is accommodated ina processing chamber, comprising: a vacuum chamber forming theprocessing chamber; an electrode portion arranged in the processingchamber; a vacuum exhaust portion for exhausting gas from the processingchamber by vacuum; a gas supply portion for supplying gas, which is usedfor generating plasma, into the processing chamber; a high frequencypower supply portion for generating plasma discharge in the processingchamber when a high frequency voltage is impressed upon the electrodeportion; a matching device for matching impedance of a plasma dischargecircuit for generating plasma discharge with impedance of the highfrequency power supply portion; and a plasma discharge state monitoringunit for monitoring a plasma discharge state in the processing chamber,the plasma discharge state monitoring unit including: a dischargedetection sensor having a plate-shaped dielectric member attached to thevacuum chamber so that one face of the plate-shaped dielectric membercan be opposed to the plasma discharge generated in the processingchamber and also having a probe electrode arranged on the other face ofthe plate-shaped dielectric member; a wave-form detecting portion forreceiving a change in electric potential induced according to a changein the plasma discharge in the probe electrode and for outputting adetection signal each time a change in electric potential agreeing witha predetermined condition appears; a plurality of counters for countingthe detection signals outputted from the wave-form detecting portion andfor holding the counted value; a counter control portion for controllingthe plurality of counters so that the counting can be executed at thetiming corresponding to a predetermined wave-form monitoring time zone;and a discharge state judgment unit for judging a state of plasmadischarge according to the counted values held by the plurality ofcounters.

According to the present invention, the plasma discharge statemonitoring unit for monitoring and judging a plasma discharge state inthe processing chamber includes: a discharge detection sensor having aplate-shaped dielectric member attached in the vacuum chamber and alsohaving a probe electrode arranged in this dielectric member; and a dataprocessing portion which receives a change in the electric potentialinduced according to a change in the plasma discharge in the probeelectrode and detects a wave-form of the change in the electricpotential of a specific pattern in a plurality of wave-form monitoringtime zones and counts the number of times of appearance of the electricpotential change waves for each type of wave-form. When a dischargestate judgment, which includes whether the discharge is executed or notand whether the discharge is executed normally or abnormally, is madeaccording to the counted value for each type of wave-form, it ispossible to highly sensitively detect a change in the plasma dischargeand rightly monitor whether the discharge is executed or not and whetherthe discharge is executed normally or abnormally.

According to the present invention, the plasma discharge state judgingunit for monitoring and judging a plasma discharge state in theprocessing chamber includes: a discharge detection sensor having aplate-shaped dielectric member attached to the vacuum chamber and alsohaving a probe electrode arranged in this dielectric member; a wave-formdetecting portion for receiving a change in the electric potentialinduced according to a change in the plasma discharge in the probeelectrode and outputting a detection signal for each appearance of achange in the electric potential conforming to a predeterminedcondition; and a plurality of counters for counting detection signalsoutputted from the wave form detecting portion and holding the countedvalue. The plurality of counters are controlled so that the counting canbe executed only at the timing corresponding to the wave-form monitoringtime zone previously set by the counter control portion. Then, a stateof the plasma discharge is judged according to the counted values heldby the plurality of counters. Due to the above constitution, onlywave-forms, which appear at the timing effective for the judgment, canbe counted in a large number of wave-form data. Accordingly, it ispossible to rightly monitor whether the plasma discharge is executed ornot and whether the plasma discharge is made normally or abnormally.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a plasma processing device ofEmbodiment 1 of the present invention.

FIG. 2 is a schematic illustration for explaining an arrangement of thedischarge detection sensor used for the plasma processing device ofEmbodiment 1 of the present invention.

FIG. 3 is a block diagram showing an arrangement of the plasma dischargestate monitoring device of the plasma processing device of Embodiment 1of the present invention.

FIG. 4A and 4B are schematic illustrations for explaining an electricpotential change wave-form and a wave-form monitoring time zone in theplasma discharge state monitoring method of Embodiment 1 of the presentinvention.

FIG. 5 is a flow chart of the discharge state judgment processingexecuted in the plasma discharge state monitoring method of Embodiment 1of the present invention.

FIG. 6 is a flow chart of the maintenance judgment processing executedin the plasma discharge state monitoring method of Embodiment 1 of thepresent invention.

FIG. 7 is a block diagram showing a constitution of the plasma dischargestate monitoring device in the plasma processing device of Embodiment 2of the present invention.

FIG. 8A and 8B are schematic illustrations for explaining an electricpotential change wave-form and a wave-form monitoring time zone in theplasma discharge state monitoring method of Embodiment 2 of the presentinvention.

FIG. 9 is a flow chart showing an electric discharge state judgmentprocessing in the plasma discharge state monitoring method of Embodiment2 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1

FIG. 1 is a sectional view showing a plasma processing device ofEmbodiment 1 of the present invention. FIG. 2 is a schematicillustration for explaining an arrangement of the discharge detectionsensor used for the plasma processing device of Embodiment 1 of thepresent invention. FIG. 3 is a block diagram showing an arrangement ofthe plasma discharge state monitoring device of the plasma processingdevice of Embodiment 1 of the present invention. FIG. 4A and 4B areschematic illustrations for explaining an electric potential changewave-form and a wave-form monitoring time zone in the plasma dischargestate monitoring method of Embodiment 1 of the present invention. FIG. 5is a flow chart of the discharge state judgment processing executed inthe plasma discharge state monitoring method of Embodiment 1 of thepresent invention. FIG. 6 is a flow chart of the maintenance judgmentprocessing executed in the plasma discharge state monitoring method ofEmbodiment 1 of the present invention.

First, referring to FIG. 1, a structure of the plasma processing devicewill be explained below. In FIG. 1, the vacuum chamber 3 is composed insuch a manner that the lid portion 2 is arranged on the horizontal baseportion 1 being freely elevated by an elevating unit (not shown). In astate in which the lid portion 2 is lowered and contacted with an upperface of the base portion 1 through the sealing member 4, the vacuumchamber 3 is put into a closed state. An air-tightly closed spacesurrounded by the base portion 1 and the lid portion 2 forms aprocessing chamber 3 a in which an object to be processed isaccommodated and subjected to plasma processing. In the processingchamber 3 a, the electrode portion 5 is arranged. The electrode portion5 is attached to the opening portion 1 a, which is provided in the baseportion 1, from the lower side through the insulating member 6. Onto anupper face of the electrode portion 5, the insulating body 7 isattached. The board 9, which is an object to be processed, is conveyedonto an upper face of the insulating body 7 in the board conveyancedirection (the direction perpendicular to the surface of the drawing)while both side end portions are being guided by the guide member 8.

The open hole 1 b provided in the base portion 1 is connected to thevent valve 12, the vacuum meter 15, the gas supply valve 13 and thevacuum valve 14 through the pipe line 11. Further, the gas supply valve13 and the vacuum valve 14 are respectively connected to the gas supplyportion 16 and the vacuum pump 17. When the vacuum valve 14 is openedwhile the vacuum pump 17 is being driven, the inside of the processingchamber 3 a is exhausted by vacuum. At this time, the degree of vacuumis detected by the vacuum meter 15. The vacuum valve 14 and the vacuumpump 17 compose a vacuum exhaust portion by which the inside of theprocessing chamber 3 a is exhausted by vacuum. When the gas supply valve13 is opened, gas used for generating plasma is supplied from the gassupply portion 16 into the processing chamber 3 a used for generatingplasma. The gas supply portion 16 has a flow rate adjusting function.Therefore, it is possible to supply an arbitrary quantity of gas usedfor generating plasma into the processing chamber 3 a. When the ventvalve 12 is opened, the atmosphere is introduced into the processingchamber 3 a at the time of breakage of vacuum.

The electrode portion 5 is electrically connected to the high frequencypower supply portion 19 through the matching device 18. When the highfrequency power supply portion 19 is driven under the condition that gasis supplied into the processing chamber 3 a after the completion ofexhaustion by vacuum, a high frequency voltage is impressed between theelectrode portion 5 and the lid portion 2 which is grounded to theground portion 10. Due to this impression of high frequency voltage,plasma discharge is generated in the processing chamber 3 a The matchingdevice 18 has a function of matching impedance of the plasma dischargecircuit, which generates plasma discharge in the processing chamber 3 a,and impedance of the high frequency power supply portion 19 with eachother.

On the side of the lid portion 2, the circular opening portion 2 a isprovided which functions as a peel-hole through which an operator canwatch the inside of the processing chamber 3 a from the outside of thevacuum chamber 3. In the opening portion 2 a, the discharge detectionsensor 23, which includes a dielectric member 21 and a probe electrodeunit 22, is fixed by the support member 24 from the outside of the lidportion 2. Referring to FIG. 2, an arrangement of the dischargedetection sensor 23 will be explained below. The dielectric member 21made of optically transparent glass is attached to the opening portion 2a provided on the lid portion 2. In the processing chamber 3 a, plasmadischarge is generated between the electrode portion 5 and the lidportion 2. The dielectric member 21 is attached to the opening portion 2a provided in the vacuum chamber 3 in a posture in which one of thefaces of the dielectric member 21 is opposed to the plasma dischargegenerated in the processing chamber 3 a.

On the other face of the dielectric member 21, that is, on the faceoutside the vacuum chamber 3, the probe electrode unit 22 is attached.The probe electrode unit 22 is an integrated component in which theprobe electrode 22 b is formed on one of the faces of the glass plate 22a and the shielding electrode 22 c is formed on the other face. When theprobe electrode unit 22 is attached to the dielectric member 21 and thedischarge detection sensor 23 is formed, under the condition that theprobe electrode 22 b is closely contacted with an outer face (the otherface) of the dielectric member 21, it is supported at the lid portion 2by the support member 24 made of conductive metal. That is, thedischarge detection sensor 23 at least includes: a plate-shapeddielectric member 21 attached to the vacuum chamber 3 so that one facecan be opposed to the plasma discharge generated in the processingchamber 3 a; and a probe electrode 22 b arranged on the other face ofthe dielectric member 21. The probe electrode 22 b is connected to theplasma monitoring device 20 through the detection lead wire 22 d.

When plasma discharge is generated in the processing chamber 3 a, theprobe electrode 22 b is electrically connected to plasma P through thedielectric member 21 and the sheath S that is a space electric chargelayer formed on an interface of the plasma P generated in the processingchamber 3 a and the dielectric member 21. That is, as shown in FIG. 2,an electric circuit is formed in which condenser C1 formed out of thedielectric member 21, condenser C2 of the capacity corresponding tosheath S and resistor R of plasma P are connected in series to eachother. In the probe electrode 22 b, an electric potential correspondingto the state of plasma P is induced. In the present embodiment, theelectric potential of the probe electrode 22 b is introduced to theplasma monitoring device 20 by the detection lead wire 22 d and a changein the electric potential corresponding to the state of plasma P ismonitored by the plasma monitoring device 20. In this way, the plasmadischarge state in the processing chamber 3 a is monitored.

In the processing chamber 3 a, when an abnormal discharge is generatedin the periphery of the board 9 mounted on the electrode portion 5, astate of plasma P generated in the processing chamber 3 a fluctuates.This fluctuation of plasma P changes the impedance of the electriccircuit described above. Therefore, this fluctuation is detected as achange in the electric potential of the probe electrode 22 b. Thischange in the electric potential is highly sensitively detected.Therefore, this detection of detecting the change in the electricpotential is characterized in that even a minute fluctuation, which canbe seldom detected by the conventional method, can be detected. Theshielding electrode 22 c has a function of electrically shielding theoutside of the probe electrode 22 b. Therefore, an electric chargegenerated in the shielding electrode 22 c is released to the lid portion2 through the conductive support member 24. Due to the foregoing, noisewith respect to the change in the electric potential induced in theprobe electrode 22 b can be reduced.

In the present embodiment, both the probe electrode 22 b and theshielding electrode 22 c are formed in such a manner that a transparentconductive material such as ITO is coated on a surface of the glassplate 22 a being formed like a film. Due to this structure, when thedischarge detection sensor 23 is attached to the opening portion 2 a, anoperator can watch the inside of the processing chamber 3 a from theoutside of the lid portion 2 through the opening portion 2 a. In thedischarge detection sensor 23 shown in the present embodiment, thedielectric member 21 is formed out of an optically transparent glassattached to the opening portion 2 a (the peep-hole) used for watchingthe inside of the processing chamber 3 a from the outside of the vacuumchamber 3 and the probe electrode 22 b is made of an opticallytransparent conductive material.

Due to the above structure, both the peep-hole for watching the insideof the processing chamber 3 a and the probe electrode 22 b formonitoring a plasma discharge state can be used at the same time. Sincethe dielectric member 21 is exposed to plasma P generated in theprocessing chamber 3 a, a surface of the dielectric member 21 isdamaged. Therefore, it is necessary to replace the dielectric member 21at a predetermined interval. Even in this case, the probe electrode unit22 and the dielectric member 21 are composed separately from each other,it is sufficient that only the dielectric member 21, which is one of theconsumable parts, is replaced and it is unnecessary to replace the probeelectrode unit 22.

The plasma processing device includes a control portion 25 forcontrolling the overall operation. When the control portion 25 controlsa vent valve 12, gas supply valve 13, vacuum valve 14, vacuum meter 15,gas supply portion 16, vacuum pump 17 and high frequency power supplyportion 19, each operation necessary for the plasma processing can becarried out. The control portion 25 controls the plasma monitoringdevice 20 and at the same time, the control portion 25 has a function ofreceiving a result of the detection obtained by the plasma monitoringdevice 20 and executing necessary control processing. The controlportion 25 includes an operation and input portion 26 and a displayportion 27. The operation and input portion 26 inputs various operationand data. The display portion 27 displays an operation image plane atthe time of the inputting operation executed by the operation and inputportion 26. Further, the display portion 27 displays a result of thejudgment made by the control portion 25 according to the result of thedetection of the plasma monitoring device 20.

Next, referring to FIG. 3, explanations will be made into theconstitution and the function of the plasma monitoring device 20 and thecontrol portion 25. In FIG. 3, the plasma monitoring device 20 includes:an AMP (amplifier) 31, an ND converter 32, a wave-form data temporarilystoring portion 33, an N-type wave-form detecting portion 34, a V-typewave form detecting portion 35, a discharge ON wave-form counter 36, adischarge OFF wave-form counter 37, an abnormal discharge wave-formcounter 38 and a leak discharge wave-form counter 39. The AMP 31amplifies a change in the electric potential of the probe electrode 22 btransmitted through the detection lead wire 22 d. The A/D converter 32A/D-converts a signal of the change in the electric potential, which isamplified by AMP 31, into an ND signal. A voltage displacement signal,which has been ND-converted by ND converter 32, that is, a digitalsignal showing a change in voltage is sent to the wave-form datatemporarily storing portion 33, the N-type wave-form detecting portion34 and the V-type wave-form detecting portion 35.

The wave-form data temporarily storing portion 33 temporarily stores adigital signal showing a change of the electric potential, which hasbeen received, as wave-form data. The N-type wave-form detecting portion34 recognizes the received digital signal as a wave-form and the thusrecognized wave-form is compared with a predetermined condition, whichhas been previously set. The N-type wave-form detecting portion 34detects an N-shaped wave-form having an N-shaped wave-form pattern. Whenthe N-shaped wave-form is detected, a detection signal is outputted eachtime of the detection. The V-type wave-form detecting portion 35recognizes the received digital signal as a wave-form in the same mannerand the thus recognized wave-form is compared with a predeterminedcondition, which has been previously set, and detects a V-shapedwave-form having a V-shaped wave-form pattern. When the V-shapedwave-form is detected, a detection signal is outputted each time of thedetection. That is, the N-type wave-form detecting portion 34 and theV-type detecting portion 35 are a plurality of wave-form detectingportions for receiving a change in the electric potential, which isinduced according to a change in the plasma discharge in the probeelectrode 22 b, and for detecting a predetermined wave-form. Both ofthem have a function of outputting a detection signal each time of theappearance of a change in the electric potential agreeing with apredetermined condition. In the N-type wave-form detecting portion 34and the V-type wave-form detecting portion 35, a predeterminedcondition, which is set for detecting a wave-form, is differentaccording to the wave-form pattern to be detected as explained below.

Referring to FIG. 4A and 4B, explanations will be made into a wave-formpattern of the wave-form detected when a change in the electricpotential is received by the discharge detection sensor 23 at the timeof operation of the plasma processing device. Explanations will be alsomade into a type of the abnormal discharge generated in the processingchamber 3 a according to the operation of the plasma processing device.FIG. 4A is a view showing a wave-form pattern detected in the processfrom the start of operation of the plasma processing device to the endof operation and also showing a predetermined time which has beenpreviously set for detecting the wave-form pattern. In this case, thepredetermined time is the first predetermined time Ta, the secondpredetermined time Tb and the third predetermined time Tc.

The time chart shown in FIG. 4B shows the setting timing of a pluralityof wave-form monitoring time zones to which a predetermined time isallotted, wherein the setting timing is shown being related to thetiming of start and end of the high frequency power supply impressionexecuted by the high frequency power supply portion 19. In this case,the wave-form monitoring time zone is set so that a time zone formonitoring and counting a detected wave-form can be specified for eachtype of wave-form. In the present embodiment, three time zones includingthe first wave-form monitoring time zone [A], the intermediate wave-formmonitoring time zone [B] and the last wave-form monitoring time zone[C], which will be explained later, are set being related to thepredetermined time described above.

First of all, the first predetermined time Ta and the thirdpredetermined time Tc are a predetermined time, which is allotted to thefirst wave-form monitoring time zone [A] for detecting a wave-formappearing at the time of the start of impression of the high frequencypower supply, and the predetermined time, which is allotted to the lastwave-form monitoring time zone [C] for detecting a wave-form appearingat the time of the end of impression of the high frequency power supply.The first wave-form monitoring time zone [A] is a time zone in which thefirst predetermined time Ta, which is set at a period of time capable ofpositively detecting a wave-form, containing an impression start timing(Concerning this timing, refer to the timing t1 showing RFon in the timechart of FIG. 4B.) of the high frequency voltage executed by the highfrequency power supply portion 19, that is, while the timing going backfrom the timing t1 by the surplus time tΔ1 is set at the starting point.The last wave-form monitoring time zone [C] is a time zone in which thethird predetermined time Tc, which is set at a period of time capable ofpositively detecting a wave-form, containing an impression end timing(Concerning this timing, refer to the timing t2 showing RFoff in thetime chart of FIG. 4B.) of the high frequency voltage executed by thehigh frequency power supply portion 19, that is, while the timing goingafter from the timing t2 by the surplus time tΔ2 is set at the startingpoint. In the first wave-form monitoring time zone [A] and the lastwave-form monitoring time zone [C], the N-type electric potential changewave-form pattern (N1-type wave-form WN1) is detected which is awave-form pattern peculiar to a change in the plasma discharge statecaused by the start and the end of the impression of the high frequencypower source, that is, which is an N-shaped wave-form pattern in whichthe electric potential deflects to both the positive and negative sideand then returns to a steady value as shown in FIG. 4A. This wave-formis detected when it is checked that the state agrees with apredetermined condition, that is, when it is checked that a change inthe electric potential detected reaches the threshold value level ±Vthwhich has been previously set on both the positive and the negativeside.

The time zone interposed between the first wave-form monitoring zone [A]and the last wave-form monitoring zone [C], that is, the intermediatewave-form monitoring zone [B], which has been set containing the secondpredetermined time tb, is a time zone corresponding to the continuationof normal operation. In this case, the appearance of an electricpotential change wave-form caused by an abnormal phenomenon is monitoredwhich is except for the electric potential change wave-form caused in anormal state change at the start and the end of impression of the highfrequency power source. That is, as showing in FIG. 4A, in theintermediate wave-form monitoring time zone [B], wave-forms appearingaccording to an abnormal discharge and a leak discharge are objects tobe monitored.

The abnormal discharge is a discharge, which is not normal, generatedbetween the board 9, which is put on the electrode portion 5, and theelectrode portion 5. The abnormal discharge is generated in the casewhere a gap is formed between the board 9 and the insulating body 7under the condition that the board 9, which is deformed being warpedbadly, is put on the electrode portion 5. In this case, as shown in FIG.4A, the electric potential change wave-form showing a change in theelectric potential with time of the probe electrode 22 b is an N-shapedelectric potential change wave-form pattern (N2-type wave-form WN2) inwhich the electric potential greatly deflects on both the positive andthe negative side and then returns to a steady value. In the same manneras that described before, the detection of this wave-form is made bychecking that the state agrees with the predetermined conditiondescribed before.

The N-type electric potential change wave-form such as an N1-typewave-form WN1 or an N2-type wave-form WN2 is chiefly detected by theN-type wave-form detecting portion 34. That is, the N-type wave formdetecting portion 34 is the first wave-form detecting portion whichreceives a change in the electric potential induced in the probeelectrode 22 b according to a change in the plasma discharge and detectsa change in the electric potential of the specific pattern generatedaccording to the above abnormal discharge. The N-type wave-formdetecting portion 34 detects an N-type electric potential changewave-form agreeing with the predetermined condition described above andoutputs a detection signal to the discharge ON wave-form counter 36, thedischarge OFF wave form counter 37 and the abnormal discharge weave-formcounter 38 which will be explained below.

In this connection, the N1-type wave-form WN1, which is detected in thefirst wave-form monitoring time zone [A] and the last wave-formmonitoring time zone [C], and the N2-type wave-form WN 2, which iscaused by an abnormal discharge, belong to the N-type electric potentialchange wave-form pattern in the same manner. However, the causes ofgeneration are different from each other. Therefore, the widths ofdeflection are greatly different from each other. In the presentEmbodiment 1, the N-type wave-forms, the widths of deflection of whichare different from each other, are detected by the same N-type wave-formdetecting portion 34.

Next, the leak discharge will be explained below. The leak discharge isa minute discharge generated between a portion such as an electrodeportion 5 or a guide member 8 provided in the processing chamber 3 aupon which a high frequency voltage is impressed and a portion in theperiphery, the electric potential of which is equal to the groundelectric potential. The leak discharge described above is generated bythe deterioration of the insulating property caused when foreign objectsgenerated by the execution of the plasma processing are attached anddeposited in the guide portion 8 for guiding the conveyance of the board9 and in the opening portion 1 a. Especially, in a portion such as aside of the guide member 8 or an inner side of the opening portion 1 afrom which the attached foreign objects can be seldom removed by thedirect injection of plasma, fine particles of resin and metal removedfrom a workpiece are easily attached and deposited. As a result, theinsulating property is deteriorated in these portions and the leakdischarge is generated between these portions and the base member 1which is grounded.

In this case, the leak discharge does not so much affect a plasmadischarge state in the processing chamber 3 a. Therefore, the electricpotential change wave-form showing an electric potential change of theprobe electrode 22 b with time becomes a V-shaped electric potentialchange wave form pattern in which the electric potential deflects onlyto the negative side and then returns to the steady value like theV-shaped wave form WV shown in FIG. 4A. This V-shaped wave-form isdetected by checking that the detected electric potential change hasreached the threshold value level ±Vth, which has been previously set onboth the positive and the negative side, only on the negative side.

This V-shaped electric potential change wave-form is chiefly detected bythe V-shaped wave-form detecting portion 35. That is, this V-shapedwave-form detecting portion 35 is the second wave-form detecting portionwhich receives an electric potential change induced according to thechange in the plasma discharge in the probe electrode 22 b in the samemanner and detects an electric potential change wave-form of thespecific pattern caused by the leak discharge described before. TheV-shaped wave-form detecting portion 35 detects a change of the aboveV-shaped electric potential change wave-form agreeing with apredetermined condition and outputs a detection signal to the leakdischarge wave-form counter 39.

When the N-shaped wave-form detecting portion 34 and the V-shapedwave-form detecting portion 35 respectively detect a specific patternwhich is an object to be detected, the N-shaped wave-form detectingportion 34 and the V-shaped wave-form detecting portion 35 respectivelyoutput a detection signal, which expresses that a wave-form of thespecific pattern has been detected, to the discharge ON wave formcounter 36, the discharge OFF wave-form counter 37, the abnormaldischarge wave-form counter 38 and the leak discharge wave-form counter39. The discharge ON wave-form counter 36, the discharge OFF wave-formcounter 37, the abnormal discharge wave form counter 38 and the leakdischarge wave form counter 39 are a plurality of counters which copewith a plurality of wave-form detecting portions (the N-shaped wave-formdetecting portion 34, the V-shaped wave-form detecting portion 35),count the detection signal outputted from the corresponding wave-formdetecting portion and hold the counted value.

First, explanations will be made into the discharge ON wave-form counter36, the discharge OFF wave form counter 37 and the abnormal dischargewave-form counter 38 which count the detection signal outputted from theN-shaped wave form detecting portion 34. The discharge ON wave-formcounter 36, the discharge OFF wave-form counter 37 and the abnormaldischarge wave-form counter 38 are a plurality of counters (the firstcounters) which count the detection signal outputted from the N-shapedwave-form detecting portion 34 and hold the counted value. The pluralityof counters record the number of times at which the N-shaped wave-formdetecting portion 34 detects N-shaped wave forms.

The wave-form monitoring time zone, in which the detection signaloutputted from the N-shaped wave-form detecting portion 34 is counted bythe plurality of counters (three counters in this case) as describedabove, is previously decided for each counter. As shown in FIG. 4B,these wave-form monitoring time zones are previously set being relatedto the impression start timing of the high frequency voltage upon theelectrode portion 5 in the plasma processing device, that is, beingrelated to the drive on/off timing of the high frequency power supplyportion 19.

The discharge ON wave form counter 36 counts a detection signal of theN1-type wave-form WN1 shown in FIG. 4A in the first wave form monitoringtime zone [A] which has been set including the impression start timingof the high frequency voltage and holds the counted value. The dischargeOFF wave-form counter 37 counts a detection signal of the N1-typewave-form WN1 shown in FIG. 4A in the last wave-form monitoring timezone [C] which has been set including the impression end timing of thehigh frequency voltage and holds the counted value. The abnormaldischarge wave-form counter 38 counts a detection signal of the N2-typewave-form WN2 shown in FIG. 4(A) in the intermediate wave-formmonitoring time zone [B] which has been set including the time zone (thesecond predetermined time Tb) interposed between the first wave-formmonitoring time zone [A] and the last wave-form monitoring time zone [C]and holds the counted value. The leak discharge wave-form counter 39 isa count portion which counts the number of times of the detection of theelectric potential change wave-form executed by the V-shaped wave-formdetecting portion 35, which is the second wave form detecting portion,and holds the counted value. The leak discharge wave-form counter 39 isthe second counter for storing the number of times at which the V-shapedwave-form detecting portion 35 detects the V-shaped wave-form WV.

The control portion 25 includes a counter control portion 41, awave-form data storing portion 42, a discharge state judging portion 43and a maintenance judging portion 44. The counter control portion 41controls a plurality of counters (the discharge ON wave-form counter 36,the discharge OFF wave-form counter 37, the abnormal discharge wave-formcounter 38) so that the detection signal can be counted only at thetiming corresponding to a previously set wave-form monitoring time zone.The counter control portion 41 is connected to the discharge ONwave-form counter 36, the abnormal discharge wave-form counter 38 andthe discharge OFF wave-form counter 37 by three counter control channelsA, B and C through the connection port 40.

As shown in FIG. 4B, when the counter control portion 41 controls thesecounters, each counter counts a detection signal outputted from theN-shaped wave-form detecting portion 34 and the V-shaped wave-formdetecting portion 35 only at the detection timing of the wave-formdetection time zone allotted to the counter concerned. Due to theforegoing, in the large number of wave-form data detected by theN-shaped wave-form detecting portion 34 and the V-shaped wave-formdetecting portion 35, only the wave-form appearing at the timingeffective for judgment can be counted. In this connection, the countercontrol channels A, B and C respectively correspond to the firstwave-form monitoring time zone [A], the intermediate wave formmonitoring time zone [B] and the last wave-form monitoring time zone[C].

The wave-form data storing portion 42 stores data for judging whether ornot the wave-form data, that is, the wave-form showing a change in theelectric potential of the probe electrode 22 b agrees with apredetermined condition to be detected by the N-shaped wave formdetecting portion 34 and the V-shaped wave-form detecting portion 35. Asthe wave-form data, an item, which characterizes the wave form patternand can be quantified, is selected such as a threshold value (Concerningthis matter, refer to the threshold value Δvth shown in FIG. 4A.) whichis set for judging a width of deflection of the electric potential inthe wave-form showing a change in the electric potential or a period oftime necessary for one deflection to be finished.

The discharge state judging portion 43 judges a state of the plasmadischarge in the processing chamber 3 a according to the counted valuesheld by a plurality of counters, that is, by the discharge ON counter36, the discharge OFF counter 37 and the abnormal discharge wave-formcounter 38. When the discharge state judging portion 43 checks thecounter values and compares each counted value with a previously setallowable value, it judges a state of the plasma discharge. Themaintenance judging portion 44 judges whether or not the maintenance isnecessary by the counted value held by the leak discharge wave-formcounter 39, that is, when the counter value is checked and compared witha previously set allowable value. Accordingly, the discharge statejudging portion 43 and the maintenance judging portion 44 compose ajudging portion for judging a state of operation of the plasmaprocessing device, that is, for judging a state of the plasma dischargeand further for judging whether or not the maintenance is necessary inthe vacuum chamber 3 according to the counted values held by thedischarge ON wave-form counter 36, the discharge OFF wave form counter37, the abnormal discharge wave-form counter 38 and the leak dischargewave-form counter 39.

In the above constitution, the discharge detecting sensor 23, the plasmamonitoring device 20 and the control portion 25 compose a plasmadischarge state monitoring unit (the plasma discharge state monitoringdevice) for monitoring a plasma discharge state in the processingchamber 3 a. The plasma monitoring device 20 receives a change in theelectric potential induced according to the change in the plasmadischarge in the probe electrode 22 b and detects an electric potentialchange wave-form of a specific pattern in the first wave-form monitoringtime zone [A] which is set including the impression start timing of thehigh frequency voltage, the last wave-form monitoring time zone [C]which is set including the impression end timing of the high frequencyvoltage and the intermediate wave-form monitoring time zone [B] which isset including a time zone interposed between the first wave-formmonitoring time zone [A] and the last wave-form monitoring time zone[C]. Further, the plasma monitoring device 20 counts the number of timesof the detection of the electric potential change wave-form for eachwave-form monitoring time zone and holds the counted value. In this way,the plasma monitoring device 20 composes a data processing portion forexecuting the processing described above. The control portion 25 is ajudgment portion for judging whether or not the plasma discharge existsand whether the plasma discharge state is normal or abnormal.

The plasma processing device is composed as described above. Next,referring to the flow chart shown in FIG. 5, the discharge statejudgment processing carried out at the time of operating this plasmaprocessing device will be explained below. In this connection, K1, K2and K3 shown in the flow chart of FIG. 5 mean counted valuesrespectively held by the discharge ON wave-form counter 36, the abnormaldischarge wave-form counter 38 and the discharge OFF wave form counter37.

When the judgment processing is started, first, the counted value K1 ofthe discharge ON wave form counter 36 is checked (ST1) and it is judgedwhether or not the counted value K1 is lower than the previously decidedallowable value 1 (ST2). In the case where the counted value K1 ishigher than the previously decided allowable value 1, it is judged thatabnormal discharge, which is not originally to be detected, isgenerated. Therefore, the abnormal discharge state is informed by thedisplay portion 27 and operation of the device is stopped (ST14). In thecase where the counted value K1 is lower than the predeterminedallowable value 1 in (ST2), the program proceeds to the next step andthe lapse of the first predetermined time Ta of the first wave-formmonitoring time zone [A] is judged (ST3). When the time has not passedyet, the program returns to (ST1) and the processing is repeated in theorder of (ST1) and (ST2).

When it is checked in (ST3) that the first predetermined time Ta haspassed, it is judged whether or not the counted value K1 is 0 (zero)(ST4). In the case where the counted value K1 is 0 (zero), it is judgedthat a positive proof of the generation of the normal plasma dischargein the processing chamber 3 a is not obtained and it is informed by thedisplay portion 27 that no plasma discharge is generated and operationof the device is stopped (ST13). Next, in the case where it is checkedin (ST4) that the counted value K1 is not 0 (zero), it is judged thatthe plasma discharge is generated in the processing chamber 3 a and theprogram proceeds to the next step. That is, the counted value K2 of theabnormal discharge wave form counter 38 is checked (ST5) and it isjudged whether or not the counted value K2 is lower than thepredetermined allowable value 2 (ST6). In the case where the countedvalue K2 is higher than the predetermined allowable value 2, it isjudged that abnormal discharge has occurred in the processing chamber 3a exceeding the allowable frequency and the abnormal discharge state isinformed by the display portion 27 and operation of the device isstopped (ST14).

In the case where the counted value K2 is lower than the predeterminedallowable value 2, the program proceeds to the next step and the lapseof the second predetermined time Tb of the intermediate wave-formmonitoring time zone [B] is judged (ST7). When the second predeterminedtime Tb has not passed yet, the program returns to (ST5) and theprocessing of (ST5) and (ST6) is repeated in order. In the case where itis checked in (ST6) that the second predetermined time Tb has passed,the program proceeds to the next step. That is, the counted value K3 ofthe discharge OFF wave-form counter 37 is checked (ST8) and it is judgedwhether or not the counted value K3 is lower than the predeterminedallowable value 3 (ST9).

In the case where the counted value K3 is higher than the previouslydecided allowable value 3, it is judged that abnormal discharge, whichis not originally to be detected, is generated. Therefore, the abnormaldischarge state is informed by the display portion 27 and operation ofthe device is stopped (ST14). In the case where the counted value K3 islower than the predetermined allowable value 3 in (ST9), the programproceeds to the next step and the lapse of the third predetermined timetc of the last wave-form monitoring time zone [C] is judged (ST10). Whenthe time has not passed yet, the program returns to (ST8) and theprocessing of (ST8) and (ST9) is repeated in order.

When it is checked in (ST10) that the third predetermined time Tc haspassed, it is judged whether or not the counted value K3 is 0 (zero)(ST11). In the case where the counted value K1 is 0 (zero), it is judgedthat a positive proof of the generation of the plasma discharge in theprocessing chamber 3 a is not obtained and it is informed by the displayportion 27 that no plasma discharge is generated and operation of thedevice is stopped (ST13). Next, in the case where it is checked in(ST11) that the counted value K3 is not 0 (zero), the plasma dischargeis normally executed (ST12). Therefore, the discharge state judgmentprocessing is finished.

The above discharge state judgment processing flow composes a method ofmonitoring a plasma discharge state in a plasma processing device formonitoring a plasma discharge state in the processing chamber 3 a in theplasma processing device for executing plasma processing for the board 9which is an object to be processed and accommodated in the processingchamber 3 a. The method of monitoring a plasma discharge state in aplasma processing device includes: a step of receiving an electricpotential change, which is induced according to a change of the plasmadischarge in the processing chamber 3 a in the probe electrode 22 b, bythe plasma monitoring device 20 which is a data processing portion; astep of detecting an electric potential change wave-form of a specificpattern by the N-type wave-form detecting portion 34 in the firstwave-form monitoring time zone [A], the last wave-form monitoring timezone [C] and the intermediate wave-form monitoring time zone [B]; a stepin which the number of times of the detection of the electric potentialchange wave-form is counted by the discharge ON wave-form counter 36,the abnormal discharge wave-form counter 38 and the discharge OFF waveform counter 37 for each wave form monitoring time zone [A], [B], [C]and the counted values K1, K2, K3 are held; and a step in which theplasma discharge state judgment, which includes the judgment ofexistence of the plasma discharge and also includes the judgment ofwhether the plasma discharge state is normal or abnormal, is executedaccording to the counted value K1, K2, K3 for each wave-form monitoringtime zone [A], [B]. [C].

Next, referring to FIG. 6, the maintenance judgment processing carriedout after the above discharge state judging processing will be explainedbelow. In this connection, K4 shown in the flow chart of FIG. 6 means acounted value held by the leak discharge wave-form counter 39. An objectof providing this maintenance judgment processing is to prevent aproblem caused when foreign objects, which are generated by the plasmaprocessing in the vacuum chamber 3 in the process of continuing theoperation of the plasma processing device, are attached and deposited.In order to accomplish the object, this maintenance judgment processingis executed by the maintenance judgment portion 44. This maintenancejudgment processing is additionally executed after the completion of(ST10) shown in the flow chart of FIG. 5.

Processing (ST20) shown in FIG. 6 is the same processing as that of(ST10) described in the explanation of FIG. 5. When the lapse of thethird predetermined time tc of the final wave-form monitoring time zone[C] is checked in (ST20), the counted value K4 of the leak dischargewave form counter 39 is checked (ST21) and it is judged whether or notthe counted value K4 is lower than the predetermined allowable value 4(ST22). In the case where the counted value K4 is lower than thepredetermined allowable value 4, it is judged that the frequency ofgeneration of the leak discharge, which is caused when foreign objectsare attached in the processing chamber 3 a, is not more than theallowable limit and it is unnecessary to execute the maintenance toremove the foreign objects. In this way, the judgment processing isfinished. On the other hand, in the case where the counted value K4 ishigher than the predetermined allowable value 4 in (ST22), it is judgedthat the frequency of generation of the leak discharge exceeds theallowable limit and there is a high possibility that foreign objects areattached and deposited. Therefore, the necessity of the maintenance isinformed by the display portion 27 (ST23).

As explained above, the plasma processing device of Embodiment 1includes a V-shaped wave-form detecting portion 35 which is the secondwave-form detecting portion in which a change in the electric potential,which is induced according to the change in the plasma discharge in theprobe electrode, is received and an electric potential change wave-formof the specific pattern caused by the leak discharge is detected.Whether or not the maintenance is needed is judged according to thecounted value obtained when the leak discharge wave-form counter 39counts the number of times of detection of the electric potentialwave-form by the V-shaped wave-form detecting portion 35. That is, theleak discharge, which is closely correlated with the deposition offoreign objects, is highly sensitively detected and the degree of thedeposition of foreign objects is estimated by the accumulated frequencyof the leak discharge. Due to this constitution, as compared with theprior art in which the maintenance time is estimated by measuring aperiod of time in which a predetermined degree of vacuum is obtained atthe time of operating the device, whether or not the maintenance time,which is necessary so that the device can be maintained in the bestoperating condition, has come can be accurately judged.

Embodiment 2

FIG. 7 is a block diagram showing a constitution of the plasma dischargestate monitoring device in the plasma processing device of Embodiment 2of the present invention. FIG. 8A and 8B are schematic illustrations forexplaining an electric potential change wave-form and a wave-formmonitoring time zone in the plasma discharge state monitoring method ofEmbodiment 2 of the present invention. FIG. 9 is a flow chart showing anelectric discharge state judgment processing in the plasma dischargestate monitoring method of Embodiment 2 of the present invention.

In the present Embodiment 2, a function of the N-type wave-formdetecting portion 34 in Embodiment 1 is divided into two N-typewave-form detecting portions according to a wave form pattern of anobject to be detected, wherein one is an N1-type wave-form detectingportion 34A and the other is an N2-type wave-form detecting portion 34B.The N1-type wave-form detecting portion 34A chiefly detects a wave-formpattern of the electric potential change caused by a usual change in thestate at the start of impression of the high frequency power source andthe end of impression. The N2-type wave-form detecting portion 34Bchiefly detects a wave form pattern of the electric potential changecaused by the abnormal discharge.

In the plasma monitoring device 20 shown in FIG. 7, a detection signalsent from the N1-type wave-form detecting portion 34A is counted by thedischarge ON wave-form counter 36 and the discharge OFF wave-formcounter 37 and a detection signal sent from the N2-type wave-formdetecting portion 34B is counted by the abnormal discharge wave-formcounter 38. Except for the above points and also except for the pointthat the setting of the wave-form monitoring time zone is different atthe time of controlling the abnormal discharge wave-form counter 38 bythe counter control portion 41, that is, except for the point that theintermediate wave-form monitoring time zone [D] described later is setinstead of the intermediate wave-form monitoring time zone [B], theplasma monitoring device 20 shown in FIG. 7 is the same as the plasmamonitoring device 20 shown in FIG. 5.

Referring to FIG. 8A and 8B, functions of the N1-type wave-formdetecting portion 34A and the N2-type wave-form detecting portion 34Bwill be explained below. FIG. 8A is a view showing a wave-form patterndetected in the process from the start of operation of the plasmaprocessing device to the end of operation and also showing apredetermined time which has been set in order to detect the wave-formpattern. FIG. 8B is a time chart in which the setting timing of aplurality of wave-form monitoring time zones to which the predeterminedtime is allotted is shown being related to the timing of the start andthe end of impression of the high frequency electric power supply by thehigh frequency electric power supply portion 19.

In the same manner as that of FIG. 4A, FIG. 8A shows a wave-form patterndetected in the process from the start to the end of operation of theplasma processing device. In this case, the first predetermined time Ta,the third predetermined time Tc, the first wave-form monitoring timezone [A] and the last wave-form monitoring time zone [C] are the same asthose shown in FIGS. 4A and 4B. Therefore, the explanations are omittedhere.

In the first wave-form monitoring time zone [A] and the last wave-formmonitoring time zone [C], in the same manner as that of FIG. 4A, theN-shaped wave-form pattern (the N1-type wave form WN1) of the electricpotential change wave-form, which is caused by a normal state change atthe start and the end of impression of the high frequency power supply,is detected. A threshold value level, which is set for detecting thewave-form pattern, is set at a level corresponding to a deflection widthof the N1-type wave-form WN1, that is, a threshold value level, which isset for detecting the wave-form pattern, is set at the first thresholdvalue level ±Vth1 which is equal to the threshold value level Vth inFIG. 4A. The wave-forms caused by the start and the end of impression ofthe high frequency power supply detected by the N1-type wave-formdetecting portion 34A in the first wave-form monitoring time zone [A]and the last wave-form monitoring time zone [C] are respectively countedby the discharge ON wave-form counter 36 and the discharge OFF wave-formcounter 37.

The intermediate wave-form monitoring time zone [D] is different fromthe intermediate wave-form monitoring time zone [B] in Embodiment 1 andincludes all of the first predetermined time Ta, the secondpredetermined time Tb and the third predetermined time Tc. In this case,the intermediate wave-form monitoring time zone [D] includes a time zone(the second predetermined time Tb) interposed between the firstwave-form monitoring time zone [A] and the last wave form monitoringtime zone [C]. Further, the intermediate wave-form monitoring time zone[D] includes the first predetermined time Ta and the third predeterminedtime Tc. When the intermediate wave-form monitoring time zone [D], theobject of which is to monitor a wave-form caused by abnormal discharge,is set as described above, it is possible to monitor the generation ofabnormal discharge in all the operation time from the start to the endof the plasma processing device. Accordingly, it is possible to moreenhance the accuracy of monitoring the generation of abnormal discharge.

In the intermediate wave-form monitoring time zone [D], in the samemanner as that shown in FIG. 4A, the N2-type wave-form WN2 caused by theabnormal discharge in the processing chamber 3 a is detected by theN2-type wave-form detecting portion 34B and the V-type weave form WVcaused by the leak discharge is detected by the V-type wave-formdetecting portion 35. The threshold value level, which is set fordetecting a wave-form pattern, is set at a level corresponding to thewidth of deflection of the N2-type wave-form WN 2, that is, thethreshold value level is set at the second threshold value level ±Vth2higher than the threshold value level Vth in FIG. 4A. The N2-typewave-form WN2 caused by the abnormal discharge detected in theintermediate wave-form monitoring time zone [D] and the V-type wave-formWV caused by the leak discharge are respectively counted by the abnormaldischarge wave-form counter 38 and the leak discharge wave-form counter39.

In Embodiment 2 described above, the wave-form detecting portion fordetecting the N-type wave form includes a plurality of wave-formdetecting portions (the N1-type wave-form detecting portion 34A, theN2-type wave-form detecting portion 34B) for detecting wave-forms, thewidths of deflection of the electric potential changes of which aredifferent. Due to this constitution, when a plurality of types of waveform patterns, which are the same N-type electric potential changewave-form patterns, the deflection widths of the changes in the electricpotential of which are different from each other, are detected by aplurality of wave-form detecting portions by using different thresholdvalue levels, a plurality of types of wave-form patterns, which arewave-form patterns similar to each other, the causes of appearance ofwhich are different from each other, can be detected while the wave-formpatterns are being rightly discriminated. Accordingly, the dischargestate can be more finely monitored.

FIG. 9 shows a discharge state judging processing executed at the timeof operation of the plasma processing device in Embodiment 2. In thisconnection, in the same manner as that of FIGS. 5, K1, K2 and K3 shownin the flow chart of FIG. 9 mean counted values respectively held by thedischarge ON wave-form counter 36, the abnormal discharge wave formcounter 38 and the discharge OFF wave-form counter 37. When the judgmentprocessing is started, the counted value K2 of the abnormal dischargewave-form counter 38, the counting object of which is the intermediatewave-form monitoring time zone [D] including all ranges of the operationtime of the plasma processing device, is checked (ST31) and it is judgedwhether or not the counted value K2 is lower than the predeterminedallowable value 2 (ST32).

In the case where the counted value K2 is higher than the predeterminedallowable value 2, it is judged that abnormal discharge, which is notoriginally to be detected, is generated. Therefore, the abnormaldischarge state is informed by the display portion 27 and operation ofthe device is stopped (ST46). In the case where the counted value K2 islower than the predetermined allowable value 2 in (ST32), the programproceeds to the next step and the lapse of the first predetermined timeTa of the first wave form monitoring time zone [A] is judged (ST33).When the time has not passed yet, the program returns to (ST31) and theprocessing is repeated in the order of (ST31) and (ST32).

When it is checked in (ST33) that the first predetermined time Ta haspassed, the counted value K1 of the discharge OFF wave-form counter 37is checked (ST34) and it is judged whether or not the counted value K1is 0 (zero) (ST35). In the case where the counted value K1 is 0 (zero),it is judged that a positive proof of the generation of the plasmadischarge in the processing chamber 3 a is not obtained and it isinformed by the display portion 27 that no plasma discharge isgenerated. Then, operation of the device is stopped (ST44).

Next, in the case where it is checked in (ST35) that the counted valueK1 is not 0 (zero), it is judged that the plasma discharge is generatedin the processing chamber 3 a and the program proceeds to the next step.That is, the counted value K2 of the abnormal discharge wave formcounter 38 is checked (ST36) and it is judged whether or not the countedvalue K2 is lower than the predetermined allowable value 2 (ST37). Inthe case where the counted value K2 is higher than the predeterminedallowable value 2, it is judged that abnormal discharge, which is notoriginally to be generated, has occurred in the processing chamber 3 aand the abnormal discharge state is informed by the display portion 27and operation of the device is stopped (ST46).

In the case where the counted value K2 is lower than the predeterminedallowable value 2, the program proceeds to the next step. That is, thelapse of the second predetermined time Tb is judged (ST38). When thesecond predetermined time Tb has not passed yet, the program returns to(ST37) and the processing of (ST37) and (ST38) is repeated in order. Inthe case where it is checked in (ST38) that the second predeterminedtime Tb has passed, the program proceeds to the next step. That is, thecounted value K2 of the abnormal discharge wave-form counter 38 ischecked again (ST39) and it is judged whether or not the counted valueK2 is lower than the predetermined allowable value 2 (ST40).

In the case where the counted value K2 is higher than the predeterminedallowable value 2, it is judged that abnormal discharge, which is notoriginally to be detected, is generated exceeding the allowablefrequency. Therefore, the abnormal discharge state is informed by thedisplay portion 27 and operation of the device is stopped (ST46). In thecase where the counted value K2 is lower than the predeterminedallowable value 2 in ST40, the program proceeds to the next step and thelapse of the third predetermined time tc of the last wave-formmonitoring time zone [C] is judged (ST41). When the time has not passedyet, the program returns to (ST40) and the processing of (ST40) and(ST41) is repeated in order.

When it is checked in (ST41) that the third predetermined time Tc haspassed, the counted value K3 of the discharge OFF wave-form counter 37is checked (ST42) and it is judged whether or not the counted value K3is 0 (zero) (ST43). In the case where the counted value K3 is 0 (zero),it is judged that a positive proof of the generation of the plasmadischarge in the processing chamber 3 a is not obtained and it isinformed by the display portion 27 that no plasma discharge is generatedand operation of the device is stopped (ST44). Next, in the case whereit is checked in (ST43) that the counted value K3 is not 0 (zero), theplasma discharge is normally executed. Therefore, the discharge statejudgment processing is finished.

The above discharge state judgment processing flow composes a method ofmonitoring a plasma discharge state in a plasma processing device formonitoring a plasma discharge state in the processing chamber 3 a in theplasma processing device for executing plasma processing for the board 9which is an object to be processed and accommodated in the processingchamber 3 a. The method of monitoring a plasma discharge state in aplasma processing device includes: a step of receiving an electricpotential change, which is induced according to a change of the plasmadischarge in the processing chamber 3 a in the probe electrode 22 b, bythe plasma monitoring device 20 which is a data processing portion; astep of detecting an electric potential change wave-form of a specificpattern by the N-type wave-form detecting portion 34 in the firstwave-form monitoring time zone [A], the last wave-form monitoring timezone [C] and the intermediate wave-form monitoring time zone [D]; a stepin which the number of times of the detection of the electric potentialchange wave-form is counted by the discharge ON wave-form counter 36,the abnormal discharge wave-form counter 38 and the discharge OFFwave-form counter 37 for each wave-form monitoring time zone [A], [D],[C] and the counted values K1, K2, K3 are held; and a step in which theplasma discharge state judgment, which includes the judgment ofexistence of the plasma discharge and also includes the judgment ofwhether the plasma discharge state is normal or abnormal, is executedaccording to the counted value K1, K2, K3 for each wave-form monitoringtime zone [A], [D]. [C].

As explained above, the plasma processing device shown in Embodiment 1or 2 includes: a discharge detection sensor 23, which is a plasmadischarge state monitoring unit for monitoring and judging a plasmadischarge state in the processing chamber 3 a, having a plate-shapeddielectric member 21 attached to the vacuum chamber 3 so that one facecan be opposed to the plasma discharge generated in the processingchamber and also having a probe electrode 22 b arranged on the otherface of the dielectric member 21; and a plasma monitoring device 20,which is a data processing portion, which receives a change in theelectric potential induced according to a change in the plasma dischargein the probe electrode 22 b, detects an electric potential changewave-form of a specific pattern in a plurality of wave-form monitoringtime zones and counts the number of times of appearance of the electricpotential change wave-forms for each type of wave-form.

Due to the above constitution, it is possible to make a discharge statejudgment, which includes the judgment of whether the discharge exists ordoes not exist and whether the discharge state is normal or abnormal,according to the counted value of each type of wave-form. In thisdischarge state judgment, a change in the plasma discharge in theprocessing chamber 3 a can be highly sensitively detected by thedischarge detection sensor 23. Therefore, compared with the conventionalmethod in which an influence given to the voltage and current of thehigh frequency power supply portion by a change in the plasma dischargeis detected and also compared with the conventional method in which adischarge state is estimated when a self-bias voltage generated betweenthe electrodes by the plasma discharge is detected, it is possible tomore accurately monitor the plasma discharge state. Accordingly, evenwhen it is necessary to generate the plasma discharge in a low outputcondition, a change in the plasma discharge state can be highlyaccurately detected and it is possible to rightly monitor whether theplasma discharge exists or does not exist and whether the plasmadischarge is normal or abnormal.

INDUSTRIAL APPLICABILITY

The plasma processing device and the plasma discharge state monitoringmethod of monitoring a plasma discharge state in the plasma processingdevice of the present invention can provide advantages of rightlymonitoring whether the plasma discharge exists or does not exist andwhether the plasma discharge is normal or abnormal. Therefore, thepresent invention can be effectively applied to a field in which plasmaprocessing such as plasma cleaning is executed when an object to beprocessed such as a board is cleaned.

1. A plasma processing device for executing plasma processing for anobject to be processed which is accommodated in a processing chamber,comprising: a vacuum chamber forming the processing chamber; anelectrode portion arranged in the processing chamber; a vacuum exhaustportion exhausting gas from the processing chamber by vacuum; a gassupply portion supplying gas which is used for generating plasma, intothe processing chamber; a high frequency power supply portion generatingplasma discharge in the processing chamber when a high frequency voltageis impressed upon the electrode portion; a matching device for matchingimpedance of a plasma discharge circuit for generating plasma dischargewith impedance of the high frequency power supply portion; and a plasmadischarge state monitoring unit monitoring a plasma discharge state inthe processing chamber, the plasma discharge state monitoring unitincluding: a discharge detection sensor having a plate-shaped dielectricmember attached to the vacuum chamber so that one face of theplate-shaped dielectric member can be opposed to the plasma dischargegenerated in the processing chamber and also having a probe electrodearranged on the other face of the plate-shaped dielectric member; a dataprocessing portion operating in such a manner that when the probeelectrode receives a change in the electric potential induced accordingto a change of the plasma discharge, a wave-form of a change of electricpotential of a specific pattern is detected in each of the first waveform monitoring time zone which is set including a timing of startingthe impression of the high frequency voltage, the last wave-formmonitoring time zone which is set including a timing of the finish ofimpression of the high frequency voltage and the intermediate wave-formmonitoring time zone which is set including a time zone interposedbetween the first wave-form monitoring time zone and the last wave-formmonitoring time zone and that the number of times of detection of thewave-form of a change of the electric potential is counted for eachwave-form monitoring time zone and the counted value is held; and ajudgment portion judging a state of discharge including the judgment ofwhether or not the plasma discharge is executed and whether the plasmadischarge state is normal or abnormal.
 2. The plasma processing deviceaccording to claim 1, wherein the dielectric member is formed out of anoptically transparent glass member attached to a peep-hole through whichthe inside of the processing chamber can see from the outside of thevacuum chamber and the probe electrode is made of an opticallytransparent conductive material.
 3. A method of monitoring a plasmadischarge state in a processing chamber in a plasma processing deviceincluding a vacuum chamber forming the processing chamber; an electrodeportion arranged in the processing chamber; a vacuum exhaust portion forexhausting gas from the processing chamber by vacuum; a gas supplyportion for supplying gas, which is used for generating plasma, into theprocessing chamber; a high frequency power supply portion for generatingplasma discharge in the processing chamber when a high frequency voltageis impressed upon the electrode portion; a matching device for matchingimpedance of a plasma discharge circuit for generating plasma dischargewith impedance of the high frequency power supply portion; and adischarge detection sensor having a plate-shaped dielectric memberattached to the vacuum chamber so that one face of the plate-shapeddielectric member can be opposed to the plasma discharge generated inthe processing chamber and also having a probe electrode arranged on theother face of the plate-shaped dielectric member, wherein an object tobe processed is accommodated in the processing chamber and processed byplasma processing, the method of monitoring a plasma discharge state ina processing chamber in a plasma processing device comprising: a step inwhich a change in electric potential induced according to a change inthe plasma discharge in the probe electrode is received by a dataprocessing portion; a step in which a wave-form of a change of electricpotential of a specific pattern is detected by a wave-form detectingportion in each of the first wave-form monitoring time zone which is setincluding a timing of starting the impression of the high frequencyvoltage, the last wave-form monitoring time zone which is set includinga timing of the finish of impression of the high frequency voltage andthe intermediate wave-form monitoring time zone which is set including atime zone interposed between the first wave-form monitoring time zoneand the last wave-form monitoring time zone; a step in which the numberof times of detection of the potential change wave-form is counted foreach wave-form monitoring time zone and the counted value is held; and astep in which a plasma discharge state judgment, which includes thejudgment of whether or not the plasma discharge is executed and alsoincludes the judgment of whether the plasma discharge state is normal orabnormal, is made according to the counted value of each wave-formmonitoring time zone.
 4. A plasma processing device for executing plasmaprocessing for an object to be processed which is accommodated in aprocessing chamber, comprising: a vacuum chamber forming the processingchamber; an electrode portion arranged in the processing chamber; avacuum exhaust portion for exhausting gas from the processing chamber byvacuum; a gas supply portion for supplying gas, which is used forgenerating plasma, into the processing chamber; a high frequency powersupply portion for generating plasma discharge in the processing chamberwhen a high frequency voltage is impressed upon the electrode portion; amatching device for matching impedance of a plasma discharge circuit forgenerating plasma discharge with impedance of the high frequency powersupply portion; and a plasma discharge state monitoring unit formonitoring a plasma discharge state in the processing chamber, theplasma discharge state monitoring unit including: a discharge detectionsensor having a plate-shaped dielectric member attached to the vacuumchamber so that one face of the plate-shaped dielectric member can beopposed to the plasma discharge generated in the processing chamber andalso having a probe electrode arranged on the other face of theplate-shaped dielectric member; a wave-form detecting portion forreceiving a change in electric potential induced according to a changein the plasma discharge in the probe electrode and for outputting adetection signal each time a change in electric potential agreeing witha predetermined condition appears; a plurality of counters for countingthe detection signals outputted from the wave form detecting portion andfor holding the counted value; a counter control portion for controllingthe plurality of counters so that the counting can be executed at thetiming corresponding to a predetermined wave-form monitoring time zone;and a discharge state judgment unit for judging a state of plasmadischarge according to the counted values held by the plurality ofcounters.
 5. The plasma processing device according to claim 4, whereinat least the wave-form monitoring time zone is the first wave formmonitoring time zone which is set including a timing of starting theimpression of the high frequency voltage, the last wave-form monitoringtime zone which is set including a timing of the finish of impression ofthe high frequency voltage and the intermediate wave-form monitoringtime zone which is set including a time zone interposed between thefirst wave-form monitoring time zone and the last wave-form monitoringtime zone, and at least three counters corresponding to the respectivewave form monitoring time zones are provided.
 6. The plasma processingdevice according to claim 4, wherein the dielectric member is formed outof an optically transparent glass member attached to a peep-hole throughwhich the inside of the processing chamber can see from the outside ofthe vacuum chamber and the probe electrode is made of an opticallytransparent conductive material.